Abstract
Polystyrenes containing electronically isolated harmane, phenoxazine or carbazole rings were synthesized and characterized by NMR spectroscopy, elemental analysis and gel permeation chromatography. The new polymers represent amorphous materials of high thermal stability with glass-transition temperatures of 139–179 °C. The electron photoemission spectra of layers of the synthesized polymers showed ionization potentials of about 5.6–6.0 eV. The polymers were tested as host materials in phosphorescent green OLEDs with bis(2-phenylpyridine)(acetylacetonato)iridium(III) as the guest. The device based on polymer containing phenoxazine fragments exhibited the best overall performance with a turn-on voltage of 2.8 V, maximum photometric efficiency of about 17 cd/A and maximum brightness of 2920 cd/m2.
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